The present invention relates generally to a pack tree for transporting items upon the back of a pack animal and more particularly to a pack tree deformably adaptable for distributing the weight of a load between the front and rear haunches of horses, mules, burros, dogs, llamas and other pack animals.
The use of animals for transporting loads in the form of heavy objects contained within saddlebags, packs and other containers predate the present invention by centuries and numerous devices have heretofore been presented for distributing the weight of such loads between the front and rear haunches of pack animals. Several factors, however, have heretofore combined to preclude complete adaptability of conventional pack trees for use with a wide range of pack animals.
Protection of the pack animal necessitates a pack tree designed to concentrate the load on the parts of the back proximate the spine since these parts are more capable of bearing the strain than are the more sensitive side portions. The anatomical configuration of pack animals vary widely, however, not only among the various species, but also within a particular breed. More importantly, the anatomical configuration of a particular animal undergoes periodical changes due to growth, weight changes, muscular motion and uneven terrain. These variations necessitate pack tree construction suitable for deformably adapting to a wide range of forms yet having sufficient resilient strength to provide the prerequisite weight allocation.
Several pack trees have heretofore been known which provide a potential solution to the difficulty of carefully allocating a load by setting forth manually adjustable frames adapted to receive particular loads. Notable examples include: Anderson U.S. Pat. No. 549,420; Schaller U.S. Pat. No. 893,199; and Bader et al U.S. Pat. Nos. 1,239,755 and 1,239,756. It should be particularly noted that such devices make no provision for automatically adjusting the weight load as is required under working conditions. Moreover, these relatively heavy and complex pack trees obtain this limited adaptability and load allocation at the expense of reducing the load-carrying capacity of the pack animal.
An alternative approach, Morgan U.S. Pat. No. 751,324, avoids some of the excessive load-carrying reduction inherent to complex pack trees by providing a relatively uncomplex, combination pack and riding saddle consisting of opposing pads and at least one transverse pommel connected at respective end portions of the pads connecting them together, the pommel consisting of a horizontal loop portion at its upper end, divergent limbs at its lower portion and an integral neck connecting the loop and limbs. This device, however, is extremely limited in the number of tie-down points provided and in its ability to adapt to the wide range of back configurations presented by various pack animals. More importantly, the forms of pommel construction suggested by Morgan either tend to separate under load since no reinforcement is provided for the pommel to limit deformability or lack substantial adaptability to divergent back configurations. It is particularly important to note that elongate wood pads, such as those suggested by Morgan, must have substantial cross section in order to support a load. Accordingly, such members are unduly heavy and unable to automatically adapt to changing back configurations since their inherent rigidity precludes flexing-type partial deformation both longitudinally and transversely relative to their longest dimension. The absence of such flexing action is particularly undesireable since it permits galling of the pack animal.
Many of the objections to the Morgan pack tree are also present in the pack tree described in Swanson U.S. Pat. No. 1,928,839 which is comprised of a pair of transverse bows pivotally connected at respective end portions of a pair of sideplates. The relatively complex hinging mechanisms of the Swanson device permit some adaptability to divergent back configurations of the pack animals but unduly increase production efforts and costs. More importantly, unless relatively heavy bows are used, the device will tend to deform under load since no provision is readily available to reinforcingly limit bow deformation under loading. Swanson also recites heavy and inflexible wood bows; thus, although the pivoting action permits some automatic transverse adjustments, it fails to recognize the need for flexing deformational adjustments as are necessitated by uneven terrain, muscular interplay, varying back configurations and the like. Further, the Swanson pack tree also severely limits the number of available tie-down points.